[fix] Use process.kill to check if process is alive

Old solution spawned `ps <pid> | grep -v PID` to perform this check.

lib/forever.js

@@ -853,13 +853,18 @@ forever.checkProcess = function (pid, callback) {
     return callback(false);
   }
 
-  exec('ps ' + pid + ' | grep -v PID', function (err, stdout, stderr) {
-    if (err) {
-      return callback(false);
-    }
-
-    callback(stdout.indexOf(pid) !== -1);
-  });
+  try {
+    //
+    // Trying to kill non-existent process here raises a ESRCH - no such
+    // process exception. Also, signal 0 doesn't do no harm to a process - it
+    // only checks if sending a singal to a given process is possible.
+    //
+    process.kill(pid, 0);
+    callback(true);
+  }
+  catch (err) {
+    callback(false);
+  }
 };
 
 //
@@ -910,4 +915,4 @@ forever.columns = {
       return timespan.fromDates(new Date(proc.ctime), new Date()).toString().yellow;
     }
   }
-};
+};